Girls who start their periods at a younger age could have a higher risk of developing Type 2 diabetes in later life, a study suggests.
Researchers found those who started their menstrual cycle at the youngest ages appeared to be at highest risk.
The exact mechanisms behind the link are not known, but researchers have suggested it could be to do with higher levels of oestrogen - the main female sex hormone - found among those who start their periods earlier.
Experts examined data on more than 17,300 women aged 20 to 65 for the large US-wide study between 1999 and 2018.
All of them had specified the age at which they had started their periods - categorised as 10 or younger, 11, 12, 13, 14 and 15 or older - and they were tracked to see whether they went on to develop Type 2 diabetes.
The researchers, led by academics from Tulane University in Louisiana, found that 1,773 (10%) developed Type 2 diabetes and among this group of women 205 also reported some type of cardiovascular disease.
Statistical analysis revealed that, compared with women who had started their periods at the age of 13, earlier age at menarche (first menstrual period) was linked to a heightened risk of developing Type 2 diabetes later in life, after taking into account various factors that could also increase a person's risk including age, family history and weight.
Those who started their periods aged 10 or younger appeared to have a 32% increased risk.
And the researchers observed a 14% heightened risk among those who started their periods at age 11 and a 29% increased risk among those who started their periods aged 12.
They also found that among women with diabetes, earlier age of first period was associated with an increased risk of stroke, but not overall cardiovascular disease.
For women who were 10 or younger when they first started their periods, the risk of having a stroke was almost three-fold higher among women who had diabetes.
The authors, whose study was published in the BMJ Nutrition Prevention and Health journal, concluded: "Earlier age at menarche was associated with Type 2 diabetes among young and middle-aged women in the USA and with stroke complications among these women living with diabetes."
They added: "Earlier age at menarche may be one of early life indicators of the cardiometabolic disease trajectory in women.
"One potential pathway explanation may be that women with an earlier age at menarche are exposed to oestrogen for longer periods of time, and early menarche has been associated with higher oestrogen levels."